Optical fibers may be used to carry light emitted from a source of light or to carry light to a photo-detector. As part of this transmission, the optical axis of the optical fiber may be aligned with a preferred location in relation to the light source or the photo-detector.
The preferred location may be found by moving the fiber with respect to the light source or the photo-detector and measuring a response of the photo-detector or, alternatively, the quality or quantity of the light coupled to the fiber.
In a “force-free alignment” the light source/fiber or photo-detector/fiber pairs are aligned without being in physical contact. A small gap is maintained between the fiber and the light source or the photo-detector. The fiber is scanned across the surface of the light source or the photo-detector until a preferred location is determined. The fiber is then secured in that location by, for example, bonding.
Greater structural integrity may be obtained when the fiber is in contact with the light source or photo-detector than when there is a gap between them. Also, when the parts are in contact there is less opportunity for misalignment and/or optical losses than when the light must traverse a gap between the parts.
However, frictional forces between the fiber and the light source or photo-detector may interfere with locating the fiber when the fiber is in contact with the light source or the photo-detector. One source of interference is introduced by system elastic deformation and metal surface finish resulting in a stick-slip motion that may hinder precise alignment. System elastic deformation includes the frictional forces introduced by contact between the fiber and the light source or the photo-detector.